Mixtures of materials that include an active material component and an electrically conductive material component are useful in many applications, such as electronics, automotive and aerospace. Such mixtures of materials often benefit from some underlying structure. For example, some structural composites utilize a fibrous web or weave of material with high tensile strength to provide strength in one or two directions, embedded in a matrix material with a lower elastic modulus to provide flexibility. Another application that benefits from an underlying structure within a mixture of active and conductive materials are battery electrodes, where the active material is an energy storage material and metallic or carbon-based particles provide electrical conductivity.
Related to the underlying structure of such mixtures, the surface area of the active material or the conductive component can also be important. A high surface area can provide a high interfacial area either between the active material and the conductive material, or upon which reactions can take place. In many applications, carbon allotropes are attractive for the conductive material component in such mixed structured materials because they can be produced with high electrical and thermal conductivities, and with high surface areas.
Conventional approaches to making such composite materials include growing structured carbon allotropes (e.g., nanostructured graphene) on a substrate, and then depositing the active material component into the pores of the structured carbon material. High quality carbon allotropes require high growth temperatures (e.g., greater than 1000° C.), and therefore the choices of substrates for carbon thin films are limited to materials that can withstand these high processing temperatures.